21984447 has 4 divisors (see below), whose sum is σ = 29312600. Its totient is φ = 14656296.

The previous prime is 21984421. The next prime is 21984449. The reversal of 21984447 is 74448912.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21984447 - 2⁸ = 21984191 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21984449) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3664072 + ... + 3664077.

It is an arithmetic number, because the mean of its divisors is an integer number (7328150).

Almost surely, 2^21984447 is an apocalyptic number.

21984447 is a deficient number, since it is larger than the sum of its proper divisors (7328153).

21984447 is an equidigital number, since it uses as much as digits as its factorization.

21984447 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7328152.

The product of its digits is 64512, while the sum is 39.

The square root of 21984447 is about 4688.7575113243. The cubic root of 21984447 is about 280.1378870179.

It can be divided in two parts, 219 and 84447, that added together give a triangular number (84666 = T₄₁₁).

The spelling of 21984447 in words is "twenty-one million, nine hundred eighty-four thousand, four hundred forty-seven".